But later in the course when the different values have become much more familiar, it evolves into something much closer to this as, a recap aid:

from www.wired.com

You've labelled the "ISO' side back to front.

What damage do you fear would be done by conceding that the above is in fact a relevant communication aid?

What does that communicate ? The triangle is shaded, brighter at the top. Does that mean I use a bigger aperture along with a faster shutter speed ? And stop down while increasing the exposure duration when it's darker ? (OK, I realize that the gradient is irrelevant, but that's only because I know better; I think it's reasonable for a newbie to assume it indicates available light). How does that triangle show the relationship between settings ? It indicates the aesthetic effects of shutter speed and aperture and inaccurately indicates ISO is directly related to noise, but doesn't say anything about how any of those settings relate to exposure. It's really a very poor communication aid. I think you'd really need a three dimensional model to illustrate the effects of three different settings on resulting image brightness; a triangle has never really been relevant.